Yarn package

ABSTRACT

A process for winding yarn into a cylindrical-bodied substantially straight-ended package wherein the yarn is traverse wound in layers of helical coils on a bobbin by traversing the yarn axially through successive stroke lengths in repeating time periods to form a package and wherein two successive stroke lengths form a traverse cycle. The improvement includes the steps of progressively decreasing the stroke length to a first value then increasing the stroke length to a second value within 50 percent of the duration of each of the time periods, while varying the helix angle at least twice during a preponderance of the traverse cycles. The winding apparatus for accomplishing this includes a divided barrel cam with sliding portions that are moved axially in concert in a programmed sequence to disperse the yarn laydown at the reversals. Yarn packages of improved formation and stability are wound using the process and apparatus of this invention. The packages are formed of a plurality of layers of helical coils, wherein each coil includes successive helical and reversal portions and are characterized by having at least two inflections in the helical portions of a preponderance of the coils.

United States Patent [191 Jennings et al. [4 1 Feb. 27, 1973 YARNPACKAGE Primary Examiner-Stanley N. Gilreath [75] Inventors.2f;,Duapgnfiepningsgyifnal($33121 Attorney-Howard P. west Jr.

Sparhng, Newark, Del. ABSTRACT [73] Assignee: E. I. du Pont de Nemoursand Compally, Wilmington DeL A process for w nding yarn into a cylindrcahbodied substantially straight-ended package wherein the yarn Filed:Man! 31, 1971 is traverse wound in layers of helical coils on a bobbin[21] APP] No; 130,036 by traversing the yarn axially through successivestroke lengths in repeating time periods to form a RelatedU.S.Applieation Data package and wherein two successive stroke lengths[62] Division of Ser. No. 865,550, Oct. 13, 1969, Pat. No. a averse FThe f includes the 3 589 63L steps of progressively decreasing thestroke length to a I first value then increasing the stroke length to a521 U.S. c1 ..242/178, 242/43 sewnd Percent the dumb" each 51 rm. c1..B65h 55 04, B65h 54/28 the time Perms whlle varying the helix angle at58 Field of Search 242/17 174 175 17 177 least twice during apreponderance of the traverse Cy- 242/159, 43, 1&1 cles. The windingapparatus for accomplishing this includes a divided barrel cam withsliding portions that [56] References Cited are moved axially in concertin a programmed sequence to disperse the yarn laydown at the rever-UNITED STATES PATENTS sals. Yarn packages of improved formation andstabili- 954 344 4/1910 Rhoades ..242/l78 F sing the Pmcess andapparatus of this 2285:4338 6/1942 Jones "242/178 invention. Thepackages are formed of a plurality of 2,345,601 4/1944 Hickes layers ofhelical coils, wherein each coil includes suc- 2,388,557 11/1945 Littleet al.... ....242 43 cessive helical and reversal portions and arecharac- 2,639,872 5/1953 Hitt et al. ..242/178 terized by having atleast two inflections in the helical 3,243,948 4/ 1966 Flanigan..242/43.l portions of a preponderance of the coils, 3,310,248 3/1967Hane 1 ..242/43 3,402,898 9/ 1968 Mattingly ..242/43 7 Claims, 33Drawing Figures PATENTEDFEBZYIW 3,718,288 SHEET 10F 5 FIG-ll FIG-l2 FIG-5 49 49 2 POSITION o, CAM ANGULAR CAM DISPLACEMENT g N4 7 Hi 5 o 1 8 L1A F l 6. 7 v

8 Fl 6- 6 A a A i P 49 F L2. 36 L2. L 46 11 1 45 FIG|8 so so A AATTORNEY 4s 1 INVENTORS.

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T' T ROTATION ruff? 85 FIG-Z4 UEL DUANE JENNINGS WAYNE CLIFFORD SPARLINGATTORNEY YINVENTORS fawn 711,

YARN PACKAGE CROSS REFERENCE TO RELATED APPLICATION This is a divisionof application Ser. No. 865,550, filed Oct. 13,1969 now U.S. Pat. No.3,589,631.

BACKGROUND OF THE INVENTION This invention relates to the cross-windingof yarns and more particularly to the winding of cylindrical yarnpackages with improved formation and stability. Such packages arecommonly formed by windups employing a surface drive. The drive roll isoperated at a constant speed thus maintaining a constant surfacevelocity of the driven package despite the growth of the package as thefilamentous material is wound thereon. A camactuated reciprocatingtraverse guide may be used to lay the yarn onto the bobbin in layers ofhelical coils either directly or by means of a print roll.

Currently used high-speed winding techniques do not give completelysatisfactory package formation when attempts are made to achieveincreased package size; i.e., an increase in package defects whichinclude bulge, spiral fans, overthrown ends, and high shoulders aregenerally noted. All of these appear to be related in some way to yarnlaydown near the ends of the cylindrical yarn package.

In the past, attempts have been made to improve yarn distribution at andnear the package ends, such as by superimposing an axial reciprocationon the primary traverse stroke or by changing the length of the strokecyclically by mechanical means with essentially no change in yarn helixangle to spread out or disperse the yarn laydown at the package ends orshoulders. These and other approaches provide very limited dispersionpatterns.

SUMMARY OF THE INVENTION According to the present invention there isprovided a method of winding a surface-driven package which comprisestraversing yarn through successive stroke lengths wherein two successivestroke lengths form a traverse cycle and each stroke length isessentially equal to initial package length in a time-program having aplurality of repeating finite first periods each of which include ashorter second period in which there occurs a progressive shortening ofthe traverse stroke length to a first value less than the initial strokelength followed by a substantially instantaneous reversal of theshortening effect and a progressive increase in the stroke to a secondvalue at which it stabilizes for the remainder of each first period. Theduration of a second period never exceeds one-half the duration of afirst period and in which winding method, exclusive of the reversals,the helix angle of the wound yarn shows a variation at least twice in apreponderance of the coils.

The apparatus according to the present invention includes a barrel camwith parallel aligned guide rails and a cam follower-yarn guide betweenthe rails, in driven engagement with the cam for traversing the yarn.The cam is divided with sliding portions that are moved axially inconcert in a programmed sequence to disperse the yarn laydown at thereversals. In one embodiment the barrel cam is divided into a centralportion and a pair of end portions supported by a shaft and rotatabletherewith. The end portions are axially slidable on the shaft. The endportions have reversal cam grooves in their surface, the inwardly facingterminal ends of which are generally aligned with respective essentiallyhelical grooves of the central cam portion. Means are provided foraxially moving the end cam portions in concert toward and away from thecentral cam portion out of alignment with the grooves of the centralportion in a preselected timed sequence of events.

In another embodiment the cam is cut in half lengthwise on parting lineswhich include the axis of rotation of the cam. The cam halves areslidably mounted on the traverse shaft and spaced to permit each camhalf to move axially relative to the other.

According to this invention unique packages are formed of a plurality oflayers of helical coils wherein each coil includes successive helicaland reversal portions. There are at least two inflections in the helicalportions of each of a preponderance of the coils in the package.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic,end-elevational view of a type of windup apparatus in which the presentinvention may be used.

FIG. 2A is a longitudinal cross-section of one embodiment-of segmentedbarrel cam assembly of this invention showing cam segments and means foractuating them.

FIG. 2B is similar to FIG. 2A except that it shows a different means foractuating the cam segments.

FIG. 3 is a side elevational view of a three-piece barrel cam showingthe separate portions.

FIG. 4 is a developed view of the outer surface of the cam of FIG. 3showing cam grooves in their aligned condition.

FIG. 5 is a side-elevational view of a three-piece barrel cam showingend portions widely separated from the center portion.

FIG. 6 is a developed view of the cam of FIG. 5 showing a lack ofalignment in the cam grooves of the various portions of the cam andangled surfaces for obtaining alignment.

Fig. 7 is a side-elevational view of the three-piece cam of FIG. 5showing end portions closed upon the center portion.

FIG. 8 is a developed view of the cam of FIG. 7 showing a lack ofalignment in the cam grooves but in the opposite direction from theshowing in FIG. 6; this view also includes angled surfaces for obtainingalignment.

FIG. 9 is a side-elevational view of a three-piece barrel cam having aparting 'line which extends parallel to the cam axis of revolution.

FIG. 10 is a developed view of the cam of FIG. 9.

FIG. 11 is a fragmentary side-elevational view of the cam of FIG. 9showing one end portion separated from the center portion.

FIG. 12 is a fragmentary side-elevational view of the cam of FIG. 9showing one end portion closed upon the center portion.

FIG. 13 is a plot of traversing mechanism stroke length as ordinate VStime as abscissa showing several preferred programs of stroke lengthvariation useful in this invention.

FIG. 14 is a partial cross-sectional view representative of a yarnpackage of the prior art showing defects.

FIG. 15 is a partial cross-sectional view representative of a yarnpackage as wound by the cam as shown in FIG. 5.

FIG. 16 is a partial cross-sectional view representative of a yarnpackage as wound by the cam as shown in FIG. 7.

FIG. 17 is a partial cross-sectional view representative of a yarnpackage in which'winding is carried out both with cam end portionsalternately separated (FIG. 15) and closed (FIG. 16).

FIG. 18 is an isometric view of a traverse mechanism which employs amotor and screw arrangement for moving parts of the barrel cam.

FIG. 19 is a developed view of a yarn package.

FIGS. 20A-20E show diagrammatic representations of traverse programsused in this invention.

FIGS. 21-23 illustrate a two piece cam and developed views for long andshort stroke positions of the cam FIG. 24 is a schematic illustration ofa yarn package showing inflections in the helical portions of thewindings.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS The apparatus ofthis invention may be used in a windup of the type shown in FIG. 1 whichcomprises a cam assembly 10, a fixed drive roll 5 coupled to a motor 6,a bobbin 7 on a support 8 which is carried on a pivoted arm 9 which inturn is adapted to urge the bobbin 7 or the growing package 2 againstthe drive roll 5. A typical cam apparatus 10 of the prior art generallycomprises a barrel cam l on a shaft 11 mounted for rotation in bearingsin fixed pedestals 19 to which are secured spaced, parallel guide rails4 which hold a cam follower-traverse guide 3 in engagement with a camgroove in the barrel cam 1.

Referring to FIG. 2A, one embodiment of the cam assembly of thisinvention generally comprises a central cam portion 12 and axiallymovable cam end portions 13, 14 carried on a shaft 1 1. The central camportion is fixed to the shaft (e.g., by a press-fit) while the endportions 13, 14 are keyed for rotation with the shaft by means of keysl6 and keyseats l5 and are slidable axially. Both of the end portions13, 14 are urged away from the central portion by means of coil springs17 which engage recesses 18. The separation of the left cam end portion13 relative to the central cam portion 12 is limited by means of theannular piston 21-cylinder 20 assembly shown at the left on the fixedpedestal 19 which also carries a ball bearing 36 for supporting shaft11. Sealing of the piston 21 is effected by means of elastomeric rings22. The righthand end of the piston 21 abuts a thrust bearing 23, theopposite side of which lies against the end face of the cam end portion13. A port 24 in the pedestal 19 serves to admit pressurized air viavalve 54 (from a source not shown) to the cylinder 20 thus making itpossible to move the piston 21, the bearing 23 and the cam end portion13 to the right against the urging of the springs 17. The cam endportion 14on the right-hand end of the assembly is actuable by the samepiston 21 and cylinder 20 and a mechanism generally comprising a longbar 25, a gear 28 and a rack 31. The bar extends parallel to the shaft11 from cam end portion 13 being slidable endwise through alignedopenings 26, 27 in cam portion 12 and end portion 14. At its right endthe bar 25 has rack teeth which engage the small gear 28 which isrotatably mounted on a shaft 29, both being located in a slottedaperture in disk 30 which is secured to the shaft 11 by a means notshown. The ends of shaft 29 are fixed in disk 30. Engaging the gear 28on the side opposite from the bar 25 is a short toothed rack 31 whichabuts the end face of cam end portion 14 thus being adapted to hold itagainst the urging of springs 17.

In another embodiment, shown in FIG. 2B, the arrangement is similar tothat of FIG. 2A except that the shaft 1 1a is hollow and the bar 25a issituated inside the shaft, being provided with radial pins 25b 250 whichextend outwardly, through axially aligned, elongated slots 37 in theshaft 11a to engage the thrust bearing 23 and cam end portion 13.Another bar 25d is in endwise abutment with the first bar 25a and isassociated with a rack-pinion-rack mechanism as in the embodiment ofFIG. 2A. The limit of outward displacement of the cam end portions 13,14 relative to the center portion 12 is reached when the piston 21bottoms in the cylinder 20, i.e., with air off, the cam stroke thenbeing called normal. However, an additional mechanism is provided (FIG.2A) to permit alteration of the overall stroke of the cam assembly,comprising an axially slidable stop pin 32, a wedge 33, a screw 35 and amotor 34. If the cam stroke is to be shortened, the motor 34 is operatedat a very blow speed and in a direction to drive the wedge 33 downwardthus causing the pin 32 to move to the right where it either drives thepiston 21 to the right or acts as a stop for leftward motion of thepiston. Operating the motor in the reverse direction will, of course,withdraw the wedge, effectively lengthening the cam stroke. The motorand wedge may be operated continuously, effecting a gradual change incam stroke length, or may be stopped at any intermediate position tohold the cam stroke constant at some value less than normal as will bediscussed further, below.

Cam paths are best studied in a developed view, such as the one shown inFIG. 4, in which the outer cylindrical surface of the cam barrel of FIG.3 is unrolled to a planar representation in order to show the true pathof the entire cam groove 43. These developed views may also be viewed asa plot of cam displacement (abscissa) versus cam angular position(ordinate) and in FIG. 4 it may be seen, throughout most of the strokeof the cam, that the path follows a straight line, representative of atrue helical path. The reversal portions will be seen to follow curvingpaths which may occupy some 40 to 60 or more of cam angular travel andwhich are generally designed to accommodate the accelerations incidentto the reversal. In examining cam groove details, it should be kept inmind that the direction of motion of the cam (CW as viewed in FIG. 1) issuch that the developed cam surface of FIG. 4 appears to move downwardas shown by arrow 44; the cam follower 45 is restrained by guide railsand moves only from side-to-side along line 46.

In a typical barrel cam of about 4 inches diameter and 7 inches stroke,the straight line or helical path forms an angle of about 30 with aplane at right angles to the cam axis of revolution, the lead (advanceper revolution) of the helix being about 7.15 inches. In an embodimentof the present invention such a cam is divided into segments by cuttingit into three separate portions along lines 47 and 48 (FIGS. 3 and 4)about 1.6 inches from each reversal and in such a manner as to removeabout 0.25 inch of material from the cut, leaving a gap between segmentsof that magnitude. In general, the line of separation will be called adiscontinuity whether a gap is present or not. In an assembledcondition, as previously described, in which the end portions of the camare movable axially, with respect to the center, the cam follower willnegotiate the discontinuity or 0.25 inch gap satisfactorily but anydeparture from that magnitude of gap (by moving the end portions)demands alterations in the part of the cam groove, called the downstreampart, which the follower enters after having crossed the gap. Thus, witheach of the end portions open to about 0.4 inch axial gap (i.e., maximumcam stroke, piston 21 bottomed in cylinder the confronting portions ofthe groove will no longer be in alignment and the side or wall of thecam groove first to encounter the follower 45 as it leaves the gap andreenters the section of the cam groove on the downstream side must berelieved at the interconnecting portion as shown by line 49 in FIGS. 5and 6 which is helical but is disposed at an angle of about 36 (ascompared to 30 in the remainder of the groove). In the end portions l3,14, this relief or this helix terminates at the point or just short ofthe point at which the 30 helix would have terminated, namely, near thebeginning of the curving reversal portion of the cam. In any giventraverse cycle this cam will go through two revolutions, thus thefollower will negotiate a discontinuity at four places and the samerelief must be provided at these sites all of which are identified bylines 49 and all of which are machined at an angle of about 36. Becauseof the varying pressure angle (from 30 to 36) the cam follower will besubject to a slight increase in velocity, the effect of which will bediscussed below.

If the cam portions 13, 14 are now moved to a nearzero gap condition orclosed as shown generally in FIGS. 7 and 8 (by means of the piston 21and cylinder 20, air on) a groove misalignment will again be present andthe lower side wall of the cam groove will now be the first to encounterthe follower 45 as it negotiates the discontinuity, crossing to thedownstream side. The lower part of the cam groove wall is relieved atfour portions, each shown by a line 50 which is helical but is disposedat an angle of about 24 again extending to a point at the beginning ofthe curving reversal or slightly short of that point at the two placeswhere it occurs in the end portions 13, M and duplicated both as toangle and as to extent (measured along the stroke) in the two places ofoccurrence in the central cam portion 12. It will be realized that theseparately described features of FIGS. 5, 6, 7 and 8 are all combinedinto a single cam.

The use of an axial gap between cam portions may lead to difficulty atcam startup because the follower may not negotiate the gap properly ifit is not up to velocity as it encounters the gap. Even if the cam is upto speed, difficulty might also be experienced because ofa loss invelocity of the cam follower (due, for example, to follower-guide railfriction, yarn tension, windage, etc.). In either case, there is a riskthat the follower may not reenter the groove of the cam properly but mayhang up on a sharp corner 51 such as shown in FIGS. 3, 4 and be severelydamaged. Such a possibility is eliminated in a preferred embodiment ofcam shown in FIGS. 9, 10, called an overlapping cam, which comprises acentral portion 12a, and end portions 13a, 14a which are separated bystepped dividing lines 52 in which the surfaces 53 each intersect a partof the cam groove 43, being aligned parallel to the axis of rotation ofthe cam barrel. Use of such a construction means that there will be noactual gap or separation along the cam groove. There will bediscontinuity in the cam groove, however, which is taken into account bycutting a relief on the downstream side walls as shown at line 49a inFIG. 11 (cam portions open) and as shown at line a in FIG. 12 (camportions closed) which appear at three other places on any given camgroove, as shown in FIG. 10. These parts of the cam groove, depicted bylines 49a and 50a, may be helical, as in the first embodiment, and arecut at like angle (say about 24 and 36) relative to a plane at rightangles to the cam axis of rotation to the same exten (measured along thestroke).

In operating the traverse mechanism the motions of the end portions 13,14 of the cams may be programmed as shown in the plot of stroke length Lversus time shown in FIG. 13 in which L is the maximum stroke length andL is the minimum stroke length (air on, cam portions closed), t is thecycle time, in seconds, and t (which is part of time t is the durationof a single period in which the cam end portions are driven in and outagain. Under practical conditions of winding the following values may beused:

L equals 0.8 to 0.98 L, preferably about 0.85 to 0.9

t equals 0.1 to 0.5 t,, preferably about 0.25 t

t equals 2 to 25 seconds, preferably 2 to 5.

Successive periods t, need not necessarily be of equal duration. Inoperating a windup and a traverse mechanism as described above,advancing yarn 38 is carried through the traversing guide 3, around thedrive roll 5 and is strung-up and deposited on the bobbin 7 while thetraversing mechanism is cycled. For example, using the program shown inFIG. 13, the timing device 56 functions continuously operating the valve54 through which air is admitted to the cylinder 20 (air on) via theconduit and throttling orifice 55 which regulates the rate at which airenters and leaves the cylinder, which in turn regulates the rate ofaxial movement of the piston 21 and earns. Air is permitted to flow tothe cylinder for time at the end of which time period the traversestroke reaches a first value (length L but only for an instant whereuponthe timing device 56 actuates the three-way valve 54, shutting off theair supply and connecting the cylinder to the exhaust port. Thethrottling orifice 55 now regulates the out-flow of air from thecylinder, which occurs in a period of about k t during which thetraverse stroke returns to a value L in this case the maximum traversestroke length. The winding continues at the maximum traverse stroke L,for a time period (l -t until the timing device again actuates valve 54to admit air to the cylinder after which the cycle is repeatedthroughout the winding of the package.

In the discussion of the helical portions of the cam grooves it will berecalled that most of the central cam portion was out at a constantangle (e.g., 30") while certain of the reliefs were cut at differentangles (e.g., 24 and 36) both in the central cam portion and in the endportions short of the reversals. Since the angles of the cam differ, itfollows that the velocity of the cam follower-traverse guide will differeach time the follower is driven by a different part of the cam. Thus,using the 30 part of the cam as a basis of comparison, at low cam angles(24) the rate (velocity) of traverse will be lower and at high camangles (36) the rate (velocity) of traverse will be higher. Generallyspeaking, this means that at low cam angles (24) more yarn will bedeposited on the package per unit length of package measured axiallythereof than when in the 30 part of the cam, and at high cam angles (36)less yarn per unit length of package will be deposited than when in the30 part of the cam. The foregoing effect is illustrated diagrammaticallyin FIGS. and 16, both of which show partial cross-sections of packages.

Referring to FIG. 15 which is related to the developed cam profile ofFIG. 6, and further taking a single revolution of the cam from point Ato point B (FIG. 6), the effect of changing rate of deposition of theyarn on the package will be seen in FIG. 15 where the high velocity oftraverse of the reliefs 49 results in the deposition of less yarn onpart of the packages as shown by the two dips 60, the verticaldimensions of which are exaggerated for purposes of illustration.Similarly, going one additional revolution from B A, dips 60' will beproduced. Thus for one cycle of the traverse (two revolutions of thecam) it will be seen that the combined dips 60 and 60' are spaced aboutequally, measured inward from the ends of the package.

Now referring to FIG. 16, similarly related to the cam profile of FIG. 8and again in a single revolution from A to B, the effect of the lowervelocity of traverse of the relief 50 (more yarn deposited) is shown byraised bands 61 (height exaggerated), and from B to A by hands 61' whichmay be seen to be equally spaced inward from the ends of the package,however,

the spacing from the end of the package to the end of a given band 61 or61' will be seen to be greater than the corresponding spacing to thedips 60 or 60' (FIG. 15) by reason of the fact that a short cam stroke(L,) condition prevails in producing the band laydown profile of FIG. 16as compared to the full stroke (L or dip" laydown of FIG. 15.

While the foregoing discussion assumes that the cam end portions arestatic, it will be recalled, in actual winding, that the cam endportions are being moved axially during part of the time (1,). The netresult is that the bands 61 become superimposed on the clips 60more-or-less in successive wraps on the package tending to fill thelatter and produce a level" package with the exception that the timeperiod t, (short stroke L during which bands 61 may be wound is half aslong or less than half as long as the time period t (full stroke Lduring which dips 60 are wound; thus, the actual combined profile of apackage might appear as shown in FIG. 17 where slight clips 62 couldoccur except for a further leveling effect described below.

In prior art type traverse programs an inevitable decrease in velocityof traverse occurs at the ends of the stroke this being necessary in theinterest of avoiding excessive follower accelerations and excessiveloadings in the reversals. Concomitant with the reduction in traversevelocity is the laydown of a slightly greater amount of yarn per unitlength of package giving rise to the well-known shoulders 57 at each endof the package shown'in cross-section in FIG. 14. These are oftenaccompanied by bulges 58 and dips 59. In the present invention, however,the reversals, during part of the time (t,), are moved inwardly from theends of the package in successive cycles thus tending to subtract yamfrom the shoulders 57 and cause its deposit in the clips 59 therebytending to level the profile of the package as seen in cross-section.Ordinarily, however, more shortening of the traverse stroke would noteliminate the shoulders completely but would simply move the now-smallershoulders inward from the ends of the package; further in accordancewith the present invention, however, the dip 62 (FIG. 17) is availableto receive some of the shoulder yarn and does so, thereby resulting in asubstantially complete leveling of the package.

It will be realized, referring to the embodiments of FIG. 2A, 28, thatan additional stop mechanism (not shown) of the same general typeas thepin 32 and its associated wedge and drive could be employed to stop thepiston in the inward direction at a position short of that at which thecam end portions 13, 14 abut the central portion 12 (thus making itpossible to limit the stroke length L,).

In yet another embodiment, as shown in FIG. 18, the position of the camend portions and control of the limits of their motions is effected bymeans of a reversible motor 63 and driven screw 64 engaged withtraveling yokes 65 which are joined by means of pins 66 to thrust plates67 which are in abutment with thrust bearings 23 and hence cam endportions 13, 14. The extent of end-wise motion of the cam is controlledby slidable electrical limit switches 68 (which reverse the motor 63)each of which switches may be independently slidable to provide long orshort strokes of the mechanism, for example, by means of individualreversible motor 69 and screws 70 drives. Cycling of this apparatus iscontrolled from a timing device (now shown). The illustrated apparatusmay be employed to effect a variety of winding programs such as thoseshown in FIGS. 20A, 20B, 20C, 20D and 20B to be described. In thisdiscussion the term A L is used for convenience and is the differencebetween the greatest traverse stroke length and the smallest strokelength in a given time period t, measured at one end of the package or:

Referring to FIGS. 20A to D:

20A: stroke shortened from L, to L periodically at time periods t L andL, are each constant, thus A L is constant.

20B: stroke L is altered while A L remains constant.

This program as well as that of 20D makes it possible to taper the endof a package or to compensate for a propensity of the package to bulgeat the ends; a number of variations are possible; viz:

208(1): L, changing by equal increments in successive equal time periodst, or a straight-line program of decrease or increase in package length.

20B(2): L, changing by unequal increments in successive equal timeperiods I, or a curving program of change in package length which couldfollow a concave or a convex path.

20C: A L is varying at intervals 1, in a preselected program while L, isheid constant (thus, L is varying). The program of change in A L issusceptible to variation, viz:

20C(1):AL gradually increasing during entire period while package isbuilt from core to maximum size (thus, L becomes progressively shorter).

20C(2):AL increasing progressively for a long period (say six to tentimes t,) after which it decreases abruptly to its original value (notzero) and again increases progressively; another way of visualizing thisprogram is that a plot of the values of L will show a sawtooth patternof period of about 6t, to about lOt, in which one leg of the sawtooth isvertical.

20C(3): A L increasing progressively for a long period, then decreasingprogressively for a like period; e.g., a plot of L shows a flattenedtriangular form.

20C(4): A L varying randomly, consequently L varies randomly.

20D: Stroke L, changing while A L is also changing in which mode L,could change in a straight line path (as in FIG. 2081) or a curved path(as in FIG. 20B2) while A L could change as in 20Cl or 20C2 or 20C3 or20C4.

FIG. 20E shows a specific mode combining the changing AL of FIG. 20C, inthis case decreasing progressively (as A La, A Lb, A Lc,) to providethree shortened stroke lengths with no time pause between the completionof the second stroke and the beginning of the third. Total time for therepeating phase is designated as t,.

From the foregoing and with reference to FIGS. 19 and 24, it will berecognized that the configuration of the yarn in the package of thepresent invention is unique and novel. In substantially any package ofthe prior art, if one excludes the reversals, the path of the yarn willgenerally be seen to be helical. If a departure from a helical path ispresent, the rate of change in the slope of the helix, in a singletraverse cycle, will be almost imperceptibly small. In contrast, theyarn in the package of the present invention, again exclusive of orinwardly of the reversal regions, exhi-bits abrupt, severe and easilyperceived inflections or changes in the lay of the yarn at least twicein each of a preponderance of the coils, a coil being defined as theyarn laid down in one traverse cycle.

Referring to a three piece type cam, it should be realized that becauseparts of a cam are in motion axially, relative to other parts of thesame cam, that there will be times at which the separate cam grooveswill be perfectly aligned by which is meant that the common helices(e.g., the 30 part) of the separate cam portions are aligned along acommon tangent. At the instant of alignment, the cam follower willexperience substantially no acceleration and will behave as if beingtraversed by a prior art cam of unvarying helix angle;

thus, for a short period the yarn being wound will be laid down in anunvarying helix. For purposes of definition, in a typical cam, perfectalignment will be taken to be within plus or minus about 0.03 inchmeasured axially. Since the total movement of the cam end portion of atypical cam is about 0.5 inch, then the abovedeflned alignment willoccur in about [2(0.03 )l00/0.5] 12% of the distance traveled by the camend portion when it is moving in and another l2 percent when it ismoving out" or, since the cam end portions are moved at essentiallyconstant axial velocity, this means that the condition of alignmentoccurs in about 12 percent of the time period But time period t, onlyamounts to half or less than half of the cycle time t,; therefore, thetime period in which alignment can occur is equal to or less than A X12% 6% of t, which means that helically-laid yarn in an uninterruptedpath will appear in 6 percent or fewer than 6 percent of the layers ofyarn in the package. Conversely, yarn exhibiting perceptibleperturbations or inflections will appear in 94 percent, or more, of thelayers of yarn. This effect may be seen by examining the layers of yarnof a package which is accomplished most readily by depositing the yarnon a planar surface by rolling the package. In substantially any packageof the prior art, the yarn will appear to lie along straight line paths(except in the reversals). However, for a three piece cam in the packageof the present invention, the yarn lines exhibit two inflections in thehelical portion of the windings; i.c., as shown in FIG. 19, the yarnwill lie along two distinct and separate, generally parallel lines 71and 72 and extend between them in a reversed curve portion 73. Two suchreversed curve portions are shown in FIG. 19. Regardless of the number,each inflection 73 always occurs in less than half the length of atraverse cycle measured circumferentially of the package and usually theinflections 73 do not intrude into the yarn reversals which are ofsubstantially con stant shape throughout the package. A smaller helixangle appears at the reversal point of the inflection 73 indicating thatthe end portion of the cam was in or closed upon the central portion.Conversely, a larger angle will appear at the reversal point of aninflection on a yarn line laid down when the cam end portions are in theopen position. With reference to FIG. 24, inflections 89 in the helicalportions of the package windings of a representative package 2 areformed when the cam is in the short stroke (closed cam) position whichplaces the reversals 90 inboard of the package ends 92.

Referring to FIGS. 20131, 2082 and 20D, it will be understood, thatduring part of the winding of a particular package, the stroke L, may bereduced to the extent that the purely helical portions of the camsegments will not return to a condition of alignment during the windingof that package; this, of course, means that yarn inflections will occurin all traverse cycles after this condition is reached except that nowthe inflections will all exhibit smaller helix angles at their reversalpoints; in a package wound, in part, under these conditions the numberof cycles showing inflections will be greater than 88% for the packagetaken as a whole. These inflections not only serve to change the rate ofyarn deposition on the package but also it is noted that the need forribbon breaking cycles is reduced when winding according to thisinvention.

Polymer was prepared substantially as described in Example 1 of U.S.Pat. No. 3,416,302 and a mixed shrinkage polyamide yarn was spun. Theyarn, having a normal denier after drawing of 30, and 18 filaments, waswound according to the present invention using three-piece segmentedcams. Packages containing 3.8 lbs. of yarn were wound at 2600 yds./min.The winding mode was as shown in FIG. 20E with A L, equal to 11/32inches, A L, equal to 7/64 inches, A L equal to 1/16 inches, and t,equal to 4.8 seconds. Operation was at full stroke L, for 71 percent ofthe time cycle t,. Traverse stroke L was 7-Va inches and, for example,traverse stroke L was thus 6 7/16 inches. Packages of the same yarn,denier, and filament count were wound using the same process conditionsexcept that conventional traverse cams of fixed profile were employed inplace of the segmented cams. The maximum weight of yarn which could bewound on these packages was about 1 lbs., at which weight sloughing ofthe yarn caused winding breaks. It should be understood that polyamide.yarn of this type is difficult to wind into packages of good formationand stability because of its frictional characteristics which resultfrom the inclusion of kaolinite in the polymer and from its highfilament modulus. Larger yarn packages provide, of course, an economicadvantage to both the yarn producer and user. The appearance of packagesmade using the segmented cams was much more pleasing aesthetically thanthat of the control packages. Some of the controls showed overthrownends which are undesirable. Despite their much greater size, packageswound according to the invention had no overthrown ends, bulge wasminimized, and spiral fan defects were much less objectionable than werethe same type of defects in the control packages.

The reliefs depicted at lines 49 and 50 in FIGS. 5, 6, 7, 8 weredescribed above as being helical; however, substantially any curvecommonly used on cams could be employed, such as a harmonic or acycloidal curve.

Such curves would, of course, have to be generally tangential withadjacent portions of the cam and would be blended orfaired together, thegeneral objective being to avoid abrupt accelerations of the camfollower. While the description has been concerned primarily with camsthat require two revolutions per traverse cycle, the invention isequally applicable to cams of one revolution per cycle or three or morerevolutions per cycle. It should also be realized that the cams asdescribed are suited for one sense of rotation only (arrow 44, FIGS. 5,'1) and cannot be operated in the opposite sense.

Another embodiment shown in FIG. 21 comprehends a two-piece segmentedcam. This embodiment comprises a barrel cam cut in half length-wise onparting lines which are in a plane which includes the axis of rotationof the cam; the cam groove 85 has tapered throats 87 on the downstreamside of each parting line as seen best in the developed view of FIGS. 22and 23. It is of interest to note that the maximum width of the taperedthroat 87, measured axially at the parting line, is twice the width ofthe throat of other embodiments are slidably mounted on a shaft 77; therin 76a of the cam-half 1S spaced to permit each cam-half 0 move axiallyrelative to its neighbor. Stub shafts 78 which extend radially from theshaft 77, being secured thereto carry gears 79 which engage racks 80 inthe respective halves of the cam. 0n the cam-half shown in FIG. 21, therighthand ring 76b extends well outside the cam and carries a thrustbearing 81 which is arranged to be acted upon by a fixed air cylinder(not shown) which serves to move the cam half back and forth.

In the same recess that carries the racks are rail surfaces 82 which areengaged by bearings 83 mounted on the stub shafts 78 beneath the gears79. This mechanism serves to transmit driving torque to the cam halvesand relieves the rack and gear mechanism of any circumferentiallydirected loads. A coil spring (not shown) mounted concentrically on theshaft 77 serves to urge the rings 76a, 76b and the two cam-halvesaxially apart.

In operation, the cam halves are actuated by means similar to thoseemployed with the three-piece embodiments to provide the desiredprogram. It will be realized that packages wound with the two-piecesegmented cam will show inflections exactly twice in each of apreponderance of the traverse cycles.

Although the illustrated embodiments disclose particular arrangementsfor moving the cam ends in concert, it would also be obvious to employother arrangements. For example, separate annular piston 21 cylinder 20assemblies might be used to drive respective cam ends 13 and 14. Howeverthe time-based program of events in the winding of a particular packageshould be essentially identical for each cam end.

What is claimed is:

l. A yarn package comprising a plurality of layers of helical coils,each coil having helical and reversal curve portions, said coils beingformed by traversing yarn through successive stroke lengths to form thepackage and wherein a traverse cycle consists of two successive strokelengths, there being at least two inflections in the helical portions ineach of a preponderance of the traverse cycles throughout the package.

2. The package of claim 1, said stroke lengths being repeatedlydecreased to a first value then increased to a second value.

3. The package of claim 2, said first and second values being constantthroughout the package.

4. The package of claim 2, said second value being constant, said firstvalue varying throughout the package.

5. The package of claim 4, said second value varying regularlythroughout the package.

6. The package of claim 4, said first value varying randomly throughoutthe package.

7. The package of claim 4, said first value varying regularly throughoutthe package.

1. A yarn package comprising a plurality of layers of helical coils,each coil having helical and reversal curve portions, said coils beingformed by traversing yarn through successive stroke lengths to form thepackage and wherein a traverse cycle consists of two successive strokelengths, there being at least two inflections in the helical portions ineach of a preponderance of the traverse cycles throughout the package.2. The package of claim 1, said stroke lengths being repeatedlydecreased to a first value then increased to a second value.
 3. Thepackage of claim 2, said first and second values being constantthroughout the package.
 4. The package of claim 2, said second valuebeing constant, said first value varying throughout the package.
 5. Thepackage of claim 4, said second value varying regularly throughout thepackage.
 6. The package of claim 4, said first value varying randomlythroughout the package.
 7. The package of claim 4, said first valuevarying regularly throughout the package.